History of the World Series Format

Beginning in 1903, the World Series has taken place as an annual postseason Major League Baseball Championship contested by the winners of the respective American and National Leagues.
However, various forms of the championship game preceded its establishment, such as The Championship of the United States played in 1884 between the Providence Grays (of the National League) and the New York Metropolitan Club (of the American Association). After newspapers referred to the victorious Providence Grays as the World Champions, the name World Championship Series also began floating around in reference to the championship game. In the six years that followed, the National League and the American Association continued playing variations of the championship game, with lengths ranging from three games to fifteen. After the American Association disbanded after the conclusion of the 1891 baseball season, no championship game took place. The National League decided to aim to continue promoting the growth of the sport and the public’s interest in it, and absorbed four of the American Association’s former franchises to grow into a twelve team league itself. In the 1982 season, the National League organized a split season, in which the winning team from the first half of the season would compete against the winner from the second half of the season. However, the new structure was not well-received by fans, and the system was abandoned for the 1893 season. The next year, in 1984, William Temple, owner of the Pittsburgh Pirates, proposed a system that lay the foundation for today’s best of seven contest known as the World Series. He offered to donate a championship trophy to the victor of a seven-game series between the first and second place teams of the National League – further posing that the franchise of the winning team would also be granted 65% of the ticket sales, leaving the losing franchise with 35%. This system remained in place for three years.
In 1901, the American League was founded, becoming an immediate competitor with the National League for the attention, profits, and loyalty of baseball fans. In 1903, the two leagues agreed to a truce, baseball’s National Agreement, in which the sport’s employment, salary, and travel requirements were redefined, leading to a merger that still thrives today. The agreement further stipulated that the top American League team and the top National League team would compete each year in a championship called the World Series. The first official World Series took place in 1903 between the Boston Americans from the American League and the Pittsburgh Pirates from the National League, with the Boston Americans emerging as the victors.
The only two years since then that the World Series has not been played, and no penultimate sports award bestowed, have been the following year, 1904 – when the New York Giants, the National League champion team, declined to play the American League champions, the Boston Americans because of ongoing animosity between him and his own league’s president, Ban Johnson – and ninety year later, in 1994, when the MLB strike led to the cancellation of the World Series that year.
With the exception of the years 1903, 1919, 1920, and 1921 – when the World Series format was played in a best of nine format – every other World Series game has been played as a best of seven play-off.